Unsatisfactory sequel to "Jaws." It's been four years since the man-eating shark feasted on the resort town of Amity; suddenly a second shark stalks the waters and the terror returns. Scheider--who must by now wonder at his tendancy to attract large aquatic carnivores with lunch on their minds-- battles without his compatriots from the original. And we haven't seen the last of the mechanical dorsal fin yet; two more sequels follow.